1) We have seen exactly nothing of Yarn Yoshi since last year, and it has an approximate release date of "I don't f**king know". For all we know, they rebooted it into a 3D platformer in the vein of Sly Cooper 1.
While true, that could be said of just about any game if you're basing this off of absence and a lack of a set release date. This includes Hyrule Warriors which you're pretty convinced is coming out this year.
Not that game development is easy, but Yarn Yoshi doesn't look like an especially taxing game, less so than Hyrule Warriors anyway. Good Feel has made an aesthetically similar game before so if you're pointing to Tecmo Koei's experience with the genre to support a 2014 release of Hyrule Warriors, the same can be said of Good Feel with Yarn Yoshi.
Zelda matters more to Nintendo than Yoshi so they're less likely to rush Hyrule Warriors if it came down to that. Given how early Hyrule Warriors looked, how late it was announced last year, and how protective Nintendo is of the Zelda series (though, admittedly, not protective enough to
not attempt a hack-and-slash spinoff), I think there's reason to believe that it could slip into 2015, not that it necessarily will. And I'm not convinced Nintendo is too concerned with spacing out release dates considering how many Mario games are released so close together.